Hyphens, En dashes, Em dashes
Use a hyphen for certain compound adjectives that precede the modified noun.
examples: well-supported hypotheses
nutrient-adjusted media
In general, do not use the hyphen if the compound adjective comes after the modified noun.
example: The hypothesis was well supported.
Do not use the hyphen when the first word in the compound adjective is an adverb ending in ly.
examples: evenly spaced samples
moderately buffered solutions
Use an en dash for ranges.
examples: pages 55–60
pH 5.1–6.8
Also use an en dash for compound adjectives if the adjectives are of equal weight.
example: the oak–pine forest
Use an em dash for parenthetical information or to indicate a sudden break in thought.
example: The forest—the largest in North America—was thriving.